So an update on the 914F tear down.
At first my initial thoughts were leaning toward operator error of insufficient
engine warm up prior to T/O where the lifter to crankcase expansion lag was
causing
the lifter to not rotate; which was somewhat correct and not correct.
There is always a reason for early component failure. Determining the root cause
is not always that easy as there are often layers of factors to be thrown into
the diagnostic possibility field.
One thing noticed on the 914 while removing each lifter was how tight they each
were during extraction and insertion through the unused portion of the lifter
bore. Could this indicate the clearance upon assembly at the factory?
Some gauges were turned up on the Czech Hobbymat lathe. One gauge was made
oversize
to determine unserviceable bore sizing. The other gauge was matched to the
914's unused portion of the bore. It was a good exercise and with the added
benefit of learning how to perform 0.0005" precision passes.
In the end the gauge revealed that the engine left the factory with 0.00015"
operating
clearance. This alone would prevent the lifter spinning in the bore as
required. Introducing lifter to crankcase expansion lag would reduce this
clearance
further again. There is minor scuffing on the bore indicating metal to
metal contact binding.
With a cause now identified the lifter bores will be correctly sized and a new
set of lifters fitted and lapped to the camshaft.
Presenting the 914 CAD data into the 3D model does not bode well for the
Classic,
with the turbo compressor and induction pipe impacting the passenger footwell.
Some bits will need to find a new posting.
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=511396#511396
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